Enhanced performance of GaN-based light emitting diode with isoelectronic Al doping layer

Abstract

The effects of isoelectronic Al doping into epitaxial GaN films grown by metal organic chemical vapor deposition on sapphire substrates were investigated. It was found, based on the measured electron mobility and x-ray analysis, that there is a limiting point of the incorporation of Al into GaN in improving the crystal quality. The electron mobility of the undoped GaN film was 178 cm2 /V s and the value greatly increased to 524 cm2 /V s by doping a small amount of Al (up to 0.45% in concentration) into the GaN layer. A further increase in the Al concentration resulted in a degradation of the electron mobility, which decreased to 138 cm2 /V s when the Al concentration was 0.82%. The output power of a side view light emitting diode (LED) with the Al-doped GaN layer was estimated to be 15.76 mW at a forward current of 20 mA, which improved by 19% compared to that of a conventional LED. These results show that a small amount of Al incorporation into a GaN layer improves the electrical and optical properties of the layer, which are attributed to the reduction of Ga vacancy and associated defects, such as dislocations. © 2009 American Institute of Physics.